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Biology > Microbes in Human Welfare > Biofertilizers
Microbes in Human Welfare


Biofertilizers are the substance that contains microorganism’s living or latent cells. Biofertilizers increase the nutrients of host plants when applied to their seeds, plant surface or soil by colonizing the rhizosphere of the plant. Biofertilizers are more cost-effective as compared to chemical fertilizers.

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Over the years, chemical fertilizers have helped farmers increase crop production to meet the increasing demand. However, the overuse of these fertilizers is harmful because they cause air and water pollution; and also deplete minerals from the soil. Therefore, there is a need to now switch to organic farming which involves the use of ‘Biofertilizers’. Let’s learn more about biofertilizers and some of their types.

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‘Bio’ means ‘life’. Therefore, by definition biofertilizers are living organisms that enrich the nutrient quality of the soil. It refers to the use of microbes instead of chemicals to enhance the nutrition of the soil. As a result, it is also less harmful and does not cause pollution.

This is what makes them so important to organic farming because they are completely environment-friendly. Let’s take a look at the different microbes that are used as biofertilizers.

Types of Biofertilizers:

  1. Bacteria
  2. Fungi
  3. Cyanobacteria


Types of Biofertilizers

You may have already studied the nitrogen-fixing nodules on the roots of legumes. This a great example of biofertilizers. The nodules are formed by the association of the bacterium ‘Rhizobium’ with the roots of these plants. This association is beneficial and is, therefore, called ‘symbiotic’.

The nodules help in fixing atmospheric nitrogen into organic forms which can then be used as nutrition by the plants. Adding Rhizobium cultures to fields has become a common practice to ensure an adequate amount of nitrogen in the soil.

Other examples of bacteria that act as biofertilizers include Azospirillum and Azotobacter. These bacteria are free-living in the soil. Azotobacter is usually used with crops like cotton, wheat, mustard, maize, etc.


Symbiotic associations exist between plants and fungi too. These associations are called ‘Mycorrhizae’. The fungus in this association absorbs phosphorus from the soil and provides it to the plant. Plants that grow with these associations also show other advantageous characteristics such as:

  1. Tolerance to drought conditions and salinity.
  2. Resistance to root-borne pathogens.
  3. An overall increase in plant growth and development.

Types of Biofertilizers


These are blue-green bacteria found in water and on land. They also help fix atmospheric nitrogen. Examples are Oscillatoria, Nostoc, Anabaena etc. The symbiotic association between the aquatic fern Azolla and Anabaena is very important for rice fields. In this association, Anabaena receives carbon and nitrogen from the plant in exchange for fixed nitrogen. This adds organic matter to the soil enhancing the fertility of rice fields.

Types of Biofertilizers

Nowadays, many biofertilizers are commercially available in the market for farmers to buy and use. These not only help replenish the soil nutrients but also reduce the dependency on chemical fertilizers. This helps in maintaining the mineral content of the soil and reduces pollution to a great extent.

Solved Example For You

Question: Which of these biofertilizers provide phosphorus to the plants?

  1. Oscillatoria
  2. Rhizobium
  3. Nostoc
  4. Mycorrhizae

Solution: The correct answer is option “d”. Mycorrhizae provides phosphorus to the plants while the others fix atmospheric nitrogen that can be used by the plants.

FAQ’s for You

Q1. What are the main sources of biofertilizers?

Answers: Biofertilizer is a type of fertilizer containing living microorganisms, that enrich the nutrient quality of the soil. The main sources of biofertilizers are bacteria, fungi, and cyanobacteria (blue-green algae). They form a symbiotic relationship with plants, in which the partners derive benefits from each other.

Q2. Discuss the role of microbes are biofertilizers.

Answers: Biofertilizers are the living microorganisms that help in the growth and development of plants or crops by enhancing the availability and supply of primary nutrients to the plant. Rhizobia are the bacteria that help in the nitrogen fixation and thus help in replenishing soil nutrients and act as biofertilizers.

Q3. Most famous nitrogen fixing bacterium/biofertilizer is?

Answer: Rhizobium is the most well-known species of a group of bacteria that acts as the primary symbiotic fixer of nitrogen. These bacteria can infect the roots of leguminous plants, leading to the formation of lumps or nodules where the nitrogen fixation takes place.

Q4. Biofertilizers are helpful because?

Answers: Biofertilizer is a substance that contains living organisms which is used to increase the fertility of the soil. It improves the growth of the plant by increasing the content of the soil and thereby increasing the availability of a variety of nutrients to the host plant. It is preferred over chemical fertilizers because it causes very less pollution. Also, it does not allow pathogens to flourish. Various biofertilizers are Rhizobium, Azotobacter, blue-green algae (BGA).

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